This doctrine has many implications, of which two are not to be missed. The first implication is the most familiar: some pleasurable experiences bring with them more pain than they are worth. That point may seem obvious, but it is clear that many of us need constant reminders! The second point comes first in position, but is frequently overlooked or downplayed because people who look to religion or "virtue" find it unattractive: No pleasure is a bad thing in itself. The reason for this statement is that as Epicurus points out, Nature gives living things only one test - the feeling of pleasure or pain - for whether a thing is ultimately "bad" or "good." If a thing is pleasurable, then we know that by Nature, and the feeling of pleasure is itself the ultimate judge of what is "good."
The issue, as Epicurus points out, is not that there is a list or ranking, either by the gods or by "reason" of "things which are good" and "things which are bad." The issue is instead, and simply, that the pursuit of some experiences which are good/pleasurable brings more experiences that are bad/pain than they are worth to us.
Epicurus has previously in the Principal Doctrines pointed out that Pleasure should not be thought of as insatiable and therefore rejected as the goal of life. A life of pleasure is a reasonable goal because it is attainable: Pleasure has a natural limit, in that when our experience is filled with pleasure, no greater pleasure can be experienced - the content of our experience (seen as a vessel) is then full, and only the details can be varied. Here Epicurus tells as that any and all pleasures are good, and can theoretically be part of that full pleasure experience, but that some pleasures, if chosen, will make detract from optimum pleasure, because they bring more pain than they are worth.
The point that some pleasures bring more pain than they are worth is one we need to constantly remember, but most of us understand it and appreciate that it is without question true.
The point that no pleasure is intrinsically bad, however, is one that many people fail to appreciate, or worse - they reject it as incompatible with their theology or their sense of "virtue" or "being a good person." Such people want to think that there is a god, or some eternal ideal, which justifies their own ranking of activity as "morally worthy" or "morally unworthy." That is the point which most people need to really think about and let sink in. No god and no set of ideal forms validates their choice of how to live. In reality, there is only Nature, and Nature gives only pleasure and pain by which to decide how to live.
More graphics for Principal Doctrine 8 can be found here: https://www.epicureanfriends.c…egory-image-list/195-pd8/